Steam injector and heat pump device

ABSTRACT

A steam injector including an introducing portion introducing a liquid flow of a refrigerant and a steam flow of the refrigerant; a mixing portion that has a shape with an internal cross-sectional area decreasing toward a moving direction of the liquid flow, and internally mixes the jet-like liquid flow with the steam flow to form a refrigerant flow; a throat portion formed on an outlet side of the mixing portion; and a diffuser portion that has a shape with an internal cross-sectional area increasing from the throat portion toward a moving direction of the refrigerant flow, and discharges the refrigerant flow at an increased pressure from a discharge portion. The throat portion has an internal cross-sectional area smaller than a critical cross-sectional area at which a discharge pressure of the refrigerant flow discharged from the discharge portion nonlinearly increases when the internal cross-sectional area of the throat portion is reduced.

FIELD

The present invention relates to a steam injector and a heat pump device using the same.

BACKGROUND

Refrigeration cycles, each using an ejector, have heretofore been disclosed (for example, refer to Patent Literature 1 and Non Patent Literature 1). These refrigeration cycles have been disclosed to achieve a highly efficient refrigeration cycle with an improved coefficient of performance (COP) by using the ejector to recover, as a work of a compressor, energy that is lost as vortices at an expansion valve in a refrigeration cycle using the expansion valve.

In addition, small-size steam injectors, each having a throat portion with an inside diameter of 6.0 mm, have been disclosed (for example, refer to Non Patent Literature 2). With these steam injectors, a higher discharge pressure than a pressure of inlet steam is obtained.

CITATION LIST Patent Literature

-   -   Patent Literature 1: Japanese Patent No. 3219108 Non Patent         Literature     -   Non Patent Literature 1: “Takeuchi, et al., “The World's First         Ejector Cycle® for DENSO's Transport Refrigerator”, Denso         Technical Review, Vol. 14 (December 2009), pp. 65-75.     -   Non Patent Literature 2: Y. Abe et al., “Model development of         turbulent dispersion force for advanced two-fluid model in         consideration of bubble-liquid phase interactions”, Proceedings         of the 18th International Conference on Nuclear Engineering         (ICONE-18) ICONE18-29517, 2010.

-   Non Patent Literature 3: Narabayashi, et al., “Study on     High-Performance Steam Injector: 1st Report, Development of     Analytical Model for Characteristic Evaluation”, Transactions of the     JSME Series B, Vol. 62, No. 597, May 1996, p. 1833.

SUMMARY Technical Problem

When application of a refrigeration cycle, such as those described above, to a heat pump device is considered, a steam injector with a higher discharge pressure is desired in order to improve the energy efficiency represented by the COP.

The present invention has been made in view of the above, and aims at providing a steam injector producing a higher discharge pressure and a heat pump device using the steam injector.

Solution to Problem

In order to solve the above problems and to attain the object, a steam injector according to an aspect of the present invention includes: an introducing portion introducing a liquid flow of a refrigerant and a steam flow of the refrigerant; a mixing portion that has a shape with an internal cross-sectional area decreasing toward a moving direction of the liquid flow, and internally mixes the jet-like liquid flow with the steam flow to form a refrigerant flow; a throat portion formed on an outlet side of the mixing portion; and a diffuser portion that has a shape with an internal cross-sectional area increasing from the throat portion toward a moving direction of the refrigerant flow, and discharges the refrigerant flow at an increased pressure from a discharge portion, in which the throat portion has an internal cross-sectional area smaller than a critical cross-sectional area at which a discharge pressure of the refrigerant flow discharged from the discharge portion of the diffuser portion nonlinearly increases when the internal cross-sectional area of the throat portion is reduced.

In a steam injector according to another aspect of the present invention, the internal cross-sectional area of the throat portion is an internal cross-sectional area at which the first-order differential coefficient of a curve representing a change in the discharge pressure of the refrigerant flow with respect to a change in the internal cross-sectional area of the throat portion is smaller than zero, or the second-order differential coefficient of the curve is larger than zero.

In a steam injector according to still another aspect of the present invention, the following Expression (1) is satisfied:

P _(D)=(m _(w0) ·u _(w0))/A ₁+(m _(s0) ·u _(s0))/A ₁−(m ₁ ·u ₁)/A ₁+(1−ζ_(N))·(ρ·u ₁ ²/2)−(ζ_(T)+ζ_(D))·(ρ_(w) ·u ₁ ²/2)  (1)

where A₁ denotes the internal cross-sectional area of the throat portion; m_(w0) and u_(w0) denote a mass flow rate and a flow velocity, respectively, of the liquid flow in the introducing portion; m_(s0) and u_(s0) denote a mass flow rate and a flow velocity, respectively, of the steam flow in the introducing portion; m₁ and u₁ denote a mass flow rate and a flow velocity, respectively, of the refrigerant flow in the throat portion; ζ_(N), ζ_(T), and ζ_(D) denote pressure loss coefficients in the mixing portion, the throat portion, and the diffuser portion, respectively; ρ_(w) denotes a density of the liquid flow; and P_(D) denotes the discharge pressure of the refrigerant flow in the discharge portion.

In a steam injector according to still another aspect of the present invention, the throat portion has a circular internal cross section, and the internal cross section has a diameter of 2 mm or smaller.

In a steam injector according to still another aspect of the present invention, a diameter of the internal cross section is 1 mm or smaller.

In a steam injector according to still another aspect of the present invention, A_(s0)/A_(w0) is in a range of 7 to 30, inclusive, where A_(W0) denotes a cross-sectional area of a region in the mixing portion into which the liquid flow is introduced, and A_(s0) denotes a cross-sectional area of a region in the mixing portion into which the steam flow is introduced.

In a steam injector according to still another aspect of the present invention, the value of A_(s0)/A_(w0) is in a range of 10 to 20, inclusive.

A steam injector according to still another aspect of the present invention further includes a drain pipe formed so as to communicate inside of the mixing portion with external air.

In a steam injector according to still another aspect of the present invention, the drain pipe is provided with a check valve.

In a steam injector according to still another aspect of the present invention, the refrigerant is water or a chlorofluorocarbon-replacing material.

A steam injector according to still another aspect of the present invention includes: a plurality of unit steam injectors each serving as the above steam injector; a liquid flow passage and a steam flow passage for supplying the liquid flows and the steam flows of the refrigerant to the respective introducing portions of the corresponding unit steam injectors.

In a steam injector according to still another aspect of the present invention, the steam injector is formed by joining together a set of component members, and grooves or holes having shapes obtained by dividing the introducing portion, the mixing portion, the throat portion, and the diffuser portion into a plurality of parts thereof are formed in each of the set of component members, and the introducing portion, the mixing portion, the throat portion, and the diffuser portion are formed by the grooves or holes when the set of component members are joined together.

In a steam injector according to still another aspect of the present invention, the set of component members have a plate-like shape and are joined with one another in a stacked state, and at least two of the unit steam injectors are arranged along main surfaces of the plate-like component members.

In a steam injector according to still another aspect of the present invention, a flow passage is formed that communicates together the introducing portions of the unit steam injectors arranged along the main surfaces of the plate-like component members.

In a steam injector according to still another aspect of the present invention, the set of component members have a plate-like shape and are joined with one another in a stacked state, and at least two of the unit steam injectors are arranged along a stacking direction of the plate-like component members.

In a steam injector according to still another aspect of the present invention, a flow passage is formed that communicates together the introducing portions of the unit steam injectors arranged along the stacking direction of the plate-like component members.

In a steam injector according to still another aspect of the present invention, the set of component members are joined with one another in a stacked state, and the unit steam injectors extend along the stacking direction of the component members.

In a steam injector according to still another aspect of the present invention, the set of component members are joined together by diffusion bonding.

A heat pump device according to an aspect of the present invention includes: a compressor compressing a refrigerant; a condenser condensing the refrigerant; an evaporator evaporating the refrigerant; and the above steam injector that introduces the steam flow of the refrigerant and the liquid flow of the refrigerant, and discharges the refrigerant flow at the increased pressure from the discharge portion of the diffuser portion.

Advantageous Effects of Invention

The present invention provides an effect that a steam injector producing a higher discharge pressure and a heat pump device using the steam injector can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic structure diagram of a steam injector according to a first embodiment of the present invention.

FIG. 2 is a main part enlarged view of an introducing portion and a mixing portion in FIG. 1.

FIG. 3 is a diagram for explaining a prediction model for operating characteristics of the steam injector.

FIG. 4 is a diagram showing relations between the inside diameter of a throat portion and a discharge pressure.

FIG. 5 is a diagram showing first-order differential coefficients of curves shown in FIG. 4.

FIG. 6 is a diagram showing second-order differential coefficients of the curves shown in FIG. 4.

FIG. 7 is a diagram showing relations between the pressure of a steam flow in the introducing portion and the discharge pressure.

FIG. 8 is a diagram showing pressures of steam flows introduced during a stable operation and during an unstable operation and pressures thereof in a drain pipe.

FIG. 9 is a schematic perspective view of a steam injector according to a second embodiment of the present invention.

FIG. 10 is a plan view of a plate-like component member of FIG. 9.

FIG. 11 is a main part sectional view of the steam injector of FIG. 9.

FIG. 12 is a diagram for explaining a flow of a refrigerant.

FIG. 13 is a main part sectional view for explaining another embodiment of the introducing portion.

FIG. 14A is a schematic view for explaining the internal structure of a steam injector according to a first modification of the second embodiment.

FIG. 14B is another schematic view for explaining the internal structure of the steam injector according to the first modification.

FIG. 14C is still another schematic view for explaining the internal structure of the steam injector according to the first modification.

FIG. 14D is still another schematic view for explaining the internal structure of the steam injector according to the first modification.

FIG. 15 is a plan view of a plate-like component member of FIG. 14B.

FIG. 16 is a plan view of a plate-like component member of FIG. 14D.

FIG. 17 is a perspective view of the plate-like component member of FIG. 14B.

FIG. 18A is a schematic view for explaining the internal structure of a steam injector according to a second modification of the second embodiment.

FIG. 18B is another schematic view for explaining the internal structure of the steam injector according to the second modification.

FIG. 18C is still another schematic view for explaining the internal structure of the steam injector according to the second modification.

FIG. 18D is still another schematic view for explaining the internal structure of the steam injector according to the second modification.

FIG. 19 is a plan view of a plate-like component member of FIG. 18B.

FIG. 20 is a plan view of a plate-like component member of FIG. 18D.

FIG. 21A is a schematic view for explaining the internal structure of a steam injector according to a third modification of the second embodiment.

FIG. 21B is another schematic view for explaining the internal structure of the steam injector according to the third modification.

FIG. 21C is still another schematic view for explaining the internal structure of the steam injector according to the third modification.

FIG. 21D is still another schematic view for explaining the internal structure of the steam injector according to the third modification.

FIG. 22 is a plan view of a plate-like component member of FIG. 21B.

FIG. 23 is a plan view of a plate-like component member of FIG. 21D.

FIG. 24A is a schematic view for explaining the structure of a steam injector according to a fourth modification of the second embodiment.

FIG. 24B is another schematic view for explaining the structure of the steam injector according to the fourth modification.

FIG. 24C is still another schematic view for explaining the structure of the steam injector according to the fourth modification.

FIG. 24D is still another schematic view for explaining the structure of the steam injector according to the fourth modification.

FIG. 25A is a schematic view for explaining the structure of a plate-like component member of FIG. 24B.

FIG. 25B is another schematic view for explaining the structure of the plate-like component member of FIG. 24B.

FIG. 25C is still another schematic view for explaining the structure of the plate-like component member of FIG. 24B.

FIG. 25D is still another schematic view for explaining the structure of the plate-like component member of FIG. 24B.

FIG. 25E is a schematic view for explaining the structure of a nozzle of FIG. 24C.

FIG. 26A is a schematic view for explaining the internal structure of a steam injector according to a fifth modification of the second embodiment.

FIG. 26B is another schematic view for explaining the internal structure of the steam injector according to the fifth modification.

FIG. 26C is still another schematic view for explaining the internal structure of the steam injector according to the fifth modification.

FIG. 26D is still another schematic view for explaining the internal structure of the steam injector according to the fifth modification.

FIG. 26E is still another schematic view for explaining the internal structure of the steam injector according to the fifth modification.

FIG. 27 is a plan view of a plate-like component member of FIG. 26C.

FIG. 28 is a plan view of a plate-like component member of FIG. 26B.

FIG. 29 is a schematic view for explaining the internal structure of a steam injector according to a sixth modification of the second embodiment.

FIG. 30 is a block diagram of a heat pump device according to a third embodiment of the present invention.

FIG. 31 is a block diagram of a heat pump device according to a fourth embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

The following describes in detail embodiments of a steam injector and a heat pump device according to the present invention, with reference to the drawings. The embodiments do not limit the present invention. In the drawings, the same reference numerals are assigned to components that are the same as, or correspond to, each other. It should be noted that the drawings are schematic, and that dimensions and ratios therebetween of the respective components differ from actual values. Relations and the ratios between the dimensions also include those differing among the drawings.

To provide a steam injector producing a higher discharge pressure, the inventors of the present invention have made keen studies, and discovered for the first time that the discharge pressure of a discharged jet liquid flow rapidly increases when the area of a throat portion is reduced to a predetermined value or below. Thus, the present invention has been conceived.

First Embodiment

FIG. 1 is a schematic structure diagram of a steam injector according to a first embodiment of the present invention. As shown in FIG. 1, this steam injector 10 includes an introducing portion 1, a mixing portion 2, a throat portion 3, a diffuser portion 4, drain pipes 5, and check valves 6. The following describes the structure and operation of the steam injector 10.

The introducing portion 1 includes a nozzle-like liquid flow introducing portion 1 a for introducing a liquid flow W1 of a refrigerant and a steam flow introducing portion 1 b for introducing a steam flow S1 of the refrigerant that is formed on both sides of the liquid flow introducing portion 1 a. The liquid flow W1 is introduced in a jet-like manner by the nozzle-like liquid flow introducing portion 1 a. The refrigerant used is not particularly limited, but only needs to be a refrigerant, such as water or a chlorofluorocarbon-replacing material, which can be used in the heat pump device.

The mixing portion 2 has a shape with an internal cross-sectional area decreasing toward a moving direction of the liquid flow, that is, downward in the plane of FIG. 1. While the cross section of the mixing portion 2 is circular in the first embodiment, the cross section may have another shape, such as a rectangular shape. The mixing portion 2 is a portion in which the liquid flow is mixed with the steam flow to form a refrigerant flow in a gas-liquid mixing state. The steam flow is rapidly cooled by the liquid flow, and condenses to greatly decrease in volume, so that a negative pressure is produced in the mixing portion 2. This phenomenon increases the flow velocity of the introduced steam flow.

FIG. 2 is a main part enlarged view of the introducing portion 1 and the mixing portion 2 in FIG. 1. As shown in FIG. 2, the steam flow S1 introduced through the steam flow introducing portion 1 b joins with the jet-like liquid flow W1 introduced through the liquid flow introducing portion 1 a from the circumferential side thereof, and mixes with the liquid flow W1. A symbol C1 indicates a region in the mixing portion 2 into which the liquid flow W1 is introduced and mixed therein with the steam flow S1. The cross-sectional area of this region C1 is denoted as A_(w0). A symbol C2 indicates a region into which the steam flow S1 is introduced and mixed therein with the liquid flow W1. The cross-sectional area of this region C2 is denoted as A_(s0).

FIG. 1 will be referred to back. The throat portion 3 is formed on the outlet side of the mixing portion 2 and the inlet side of the diffuser portion 4. While the cross section of the throat portion 3 is circular in the first embodiment, the cross section may have another shape, such as a rectangular shape. The throat portion 3 is a portion extending from the mixing portion 2 to the diffuser portion 4, and is a portion having the smallest internal cross-sectional area. Accordingly, the refrigerant flow has the highest flow velocity when passing through the throat portion 3.

The diffuser portion 4 has a shape with an internal cross-sectional area increasing from the throat portion 3 toward a moving direction of the refrigerant flow. While the cross section of the diffuser portion 4 is circular in the first embodiment, the cross section may have another shape, such as a rectangular shape. The internal cross-sectional area of the diffuser portion 4 increases toward the moving direction of the refrigerant flow, so that the refrigerant flow decreases in flow velocity and increases in pressure with the movement of the refrigerant flow. As a result, the diffuser portion 4 discharges the refrigerant flow at the increased pressure as a refrigerant flow F1 from a discharge portion 4 a.

Each of the drain pipes 5 is formed so as to communicate with the outside of the mixing portion 2 from the inside thereof. The drain pipes 5 are provided with the check valves 6. The drain pipes 5 have a function to exhaust excess steam existing in the mixing portion 2. Exhausting the excess steam in this manner increases the stability of operation of the steam injector 10. While the steam injector 10 is in operation, the negative pressure is produced in the mixing portion 2, as described above. The check valves 6 serve to prevent external air from being brought into the mixing portion 2 by the negative pressure so as to increase the stability of operation of the steam injector 10.

The steam injector 10 may be provided, for example, by forming grooves or holes having shapes obtained by dividing the introducing portion 1, the mixing portion 2, the throat portion 3, the diffuser portion 4, and the drain pipes 5 into a plurality of parts thereof in each of a set of component members composed of two or more component members (such as plate-like component members), and by joining together the set of component members in which the grooves or holes are formed. In this case, each of the introducing portion 1, the mixing portion 2, the throat portion 3, the diffuser portion 4, and the drain pipes 5 is formed by combining the grooves or holes formed in the respective component members when the set of component members is joined together. The constituent material of the component members may be, for example, a resin material. However, a sufficient joining strength endurable to a high discharge pressure of the refrigerant flow F1 is obtained by making the component members from, for example, a metal, and by joining together the set of component members using, for example, diffusion bonding. The metal material constituting the component members is preferably a material, such as a stainless material, having high heat insulating properties.

In the steam injector 10 according to the first embodiment, the internal cross-sectional area of the throat portion 3 is set smaller than a predetermined critical cross-sectional area. This setting increases the discharge pressure of the refrigerant flow discharged from the discharge portion 4 a of the diffuser portion 4.

The following describes the principle of increasing the discharge pressure of the refrigerant flow, based on a prediction model for operating characteristics of the steam injector (refer to Non Patent Literature 3). FIG. 3 is a diagram for explaining the prediction model for operating characteristics of the steam injector. In FIG. 3, a symbol “0” indicates the start point of a region in which the liquid flow W1 mixes with the steam flow S1 (refer to the regions C1 and C2 in FIG. 2). A symbol “1” indicates the throat portion 3. A symbol “D” indicates the discharge portion 4 a of the diffuser portion 4. These symbols are used, where appropriate, as suffixes in expressions given below.

In this model, first, the steam flow S1 is assumed to totally condense in the throat portion 3. The steam flow S1 is also assumed to be introduced as a critical flow into the mixing portion 2, and the flow velocity of the steam flow S1 is calculated from the critical pressure. Furthermore, the flow structure and the interfacial behavior of the refrigerant flow are not taken into account.

First, expressions of the law of conservation of mass, expressions of the law of conservation of energy, and expressions of the law of conservation of momentum are applied to the liquid flow W1, the steam flow S1, and the refrigerant flow F1 in the mixing portion 2 (between “0” and “1”). In addition, a Bernoulli's equation is applied to the refrigerant flow F1 in the diffuser portion 4 (between “1” and “D”). Expression (1) below is derived from these expressions. In this case, the refrigerant was assumed to be water. Specifically, values of a water flow and a water steam flow were used as values of parameters for the liquid flow and the steam flow.

P _(D)=(m _(w0) ·u _(w0))/A ₁+(m _(s0) ·u _(s0))/A ₁−(m ₁ ·u ₁)/A ₁+(1−ζ_(N))·(ρ·u ₁ ²/2)−(ζ_(T)+ζ_(D))·(ρ_(w) ·u ₁ ²/2)  (1)

In Expression (1), A₁ denotes the internal cross-sectional area of the throat portion 3; m_(w0) and u_(w0) denote the mass flow rate and the flow velocity, respectively, of the liquid flow W1 in the introducing portion 1; m_(s0) and u_(s0) denote the mass flow rate and the flow velocity, respectively, of the steam flow S1 in the introducing portion 1; m₁ and u₁ denote the mass flow rate and the flow velocity, respectively, of the refrigerant flow F1 in the throat portion 3; ζ_(N), ζ_(T), and ζ_(D) denote the pressure loss coefficients in the mixing portion 2, the throat portion 3, and the diffuser portion 4, respectively; ρ_(w) denotes the density of the liquid flow W1; and P_(D) denotes the discharge pressure of the refrigerant flow F1 in the discharge portion 4 a. When Expression (1) was derived, A_(w0) was set to 7.54×10⁻⁷ m², and A_(s0) was set to 5.42×10⁻⁶ m². In this case, A_(s0)/A_(w0) results in approximately 7.2. A temperature T_(w0) of the liquid flow W1 in the introducing portion 1 was set to 20° C., and ζ_(s) was set to 0.37.

In Expression (1), ζ_(N) was set to 0.05, ζ_(T) to 0.1, ζ_(D) to 0.15, and m_(w0) to 1.27×10⁻² kg/s, and in each case in which a pressure P_(s) of the steam flow S1 in the introducing portion 1 is 0.10 MPa, 0.13 MPa, or 0.15 MPa, a change in the discharge pressure P_(D) with a change in an inside diameter D_(T) of the throat portion 3 from 6.0 mm to 300 μm was calculated. Here, one atmospheric pressure is 0.1024 MPa. The cross section of the throat portion 3 is assumed to be circular. In this case, the internal cross-sectional area A₁ satisfies the following: π(D_(T)/2)²=A₁.

FIG. 4 is a diagram showing relations between the inside diameter D_(T) of the throat portion 3 and the discharge pressure P_(D). FIG. 5 is a diagram showing first-order differential coefficients of curves shown in FIG. 4. FIG. 6 is a diagram showing second-order differential coefficients of the curves shown in FIG. 4. When FIGS. 4 to 6 were derived, calculations were performed by changing the value of D_(T) at increments of 0.01 mm. As shown in FIG. 4, for any value of the pressure P_(s), the discharge pressure P_(D) remained substantially constant as the inside diameter D_(T) decreased from 6.0 mm. However, an analysis using Expression (1) verified that the discharge pressure P_(D) rapidly nonlinearly increases as the inside diameter D_(T) decreases to a value (such as 600 μm) smaller than a critical value of approximately 1.0 mm, for any value of the pressure P_(s). As shown in FIG. 5, the first-order differential coefficient of each of the curves representing the relations between the inside diameter D_(T) and the pressure P_(s) shown in FIG. 4 is substantially zero when the inside diameter D_(T) is larger than 1.0 mm. However, as the inside diameter D_(T) decreases to a value smaller than the critical value of approximately 1.0 mm, the first-order differential coefficient decreases to smaller than zero and then rapidly decreases. Furthermore, as shown in FIG. 6, the second-order differential coefficient of each of the curves representing the relations between the inside diameter D_(T) and the pressure P_(s) shown in FIG. 4 is substantially zero when the inside diameter D_(T) is larger than 1.0 mm. However, as the inside diameter D_(T) decreases to a value smaller than the critical value of approximately 1.0 mm, the second-order differential coefficient increases to larger than zero and then rapidly increases.

Based on these results, the steam injector 10 according to the first embodiment produces a conventionally unattainable high discharge pressure by setting the inside diameter D_(T) or the internal cross-sectional area A₁ of the throat portion 3 to an inside diameter or an internal cross-sectional area smaller than the critical value (of the inside diameter or the cross-sectional area) below which the discharge pressure P_(D) increases. When the inside diameter or the cross-sectional area is smaller than the critical value, the first-order differential coefficient of the curve representing the change in the discharge pressure P_(D) with respect to the change in the inside diameter D_(T) or the internal cross-sectional area A₁ of the throat portion 3 (that is, the curve shown in FIG. 4) is smaller than zero. The second-order differential coefficient is larger than zero. Accordingly, a high discharge pressure P_(D) is obtained by employing the inside diameter D_(T) or the internal cross-sectional area A₁ at which the first-order or second-order differential coefficient changes from zero.

In FIGS. 4, 5, and 6 referred to above, when the inside diameter D_(T) is larger than the critical value, the discharge pressure P_(D) is substantially constant, and the first-order and second-order differential coefficients of the curves representing the change in the discharge pressure PO are substantially zero. Accordingly, the critical value can be defined as a value at or below which the first-order or second-order differential coefficient changes from zero. When the inside diameter D_(T) is smaller than the critical value, the discharge pressure P_(D) may not be substantially constant, and the first-order and second-order differential coefficients of the curves representing the change in the discharge pressure Pr may not be zero, in some cases. In such cases, the critical value may be defined to be a value at which the second-order differential coefficient increases by 10% or more as the inside diameter D_(T) or the internal cross-sectional area A₁ decreases. For example, if the second-order differential coefficient increases by 10%, from 1.0 to 1.1, as the inside diameter D_(T) decreases from 1.0 mm to 0.9 mm, the critical value of the inside diameter D_(T) may be defined to be 1.0 mm.

The critical value (of the inside diameter or the cross-sectional area) at which the discharge pressure Pr increases changes with the values of the parameters included in Expression (1). Accordingly, a high discharge pressure P_(D) as an effect of the present invention can be obtained by setting the inside diameter D_(T) or the internal cross-sectional area A₁ of the throat portion 3 so as to be smaller than the critical value, taking the values of the parameters into account. For example, if the refrigerant is not water but another refrigerant, the inside diameter D_(T) or the internal cross-sectional area A₁ of the throat portion 3 only needs to be set by replacing the parameters for the water with parameters for the refrigerant to be used.

Then, in Expression (1), the internal cross-sectional area A₁ of the throat portion 3 was set to 2.83×10⁻⁷ m² (equivalent to the inside diameter D_(T) of 600 μm), and in each case in which m_(w0) is 1.27×10⁻² kg/s, 1.43×10⁻² kg/s, or 1.59×10⁻² kg/s, a change in the discharge pressure P_(D) with a change in the pressure P_(s) of the steam flow S1 in the introducing portion 1 was calculated.

FIG. 7 is a diagram showing relations between the pressure P_(s) of the steam flow S1 in the introducing portion 1 and the discharge pressure P_(D). As shown in FIG. 7, an analysis using Expression (1) verified that the discharge pressure P_(D) can increase as the pressure P_(s) increases.

Then, steam injectors were actually made using a resin material, and experiments demonstrating the operation of the steam injectors were conducted. Seven types of the steam injectors were made. Specifically, the seven types include a type (Sample 1) that has the same structure as that of the first embodiment shown in FIG. 1 and in which A_(s0)/A_(w0) is 36.2, a type (Sample 2) that has the same structure as that of Sample 1 except for not being provided with the check valves, and a type (Sample 3) that has the same structure as that of Sample 1 except for not being provided with the check valves and the drain pipes. The seven types also include a type (Sample 4) that has the same structure as that of the first embodiment shown in FIG. 1 and in which A_(s0)/A_(w0) is 7.2, a type (Sample 5) that has the same structure as that of Sample 1 except for not being provided with the check valves, and a type (Sample 6) that has the same structure as that of Sample 1 except for not being provided with the check valves and the drain pipes. The seven types further include a type (Sample 7) that is obtained by adding a mechanism capable of varying A_(s0)/A_(w0) to the same structure as that of the first embodiment shown in FIG. 1. Such a variable mechanism can be obtained by structuring the steam injector so as to be capable of varying the amount of projection of the liquid flow introducing portion 1 a into the mixing portion 2.

As a structure common to Samples 1 to 7, the length of the mixing portion 2 was set to 22.5 mm, the inside diameter of the mixing portion 2 on a side opposite to the throat portion 3 to 3.4 mm, the cross-sectional area A_(w0) for introducing the liquid flow W1 to 1.94 m² (equivalent to an inside diameter of 1.57 mm), the inside diameter D_(T) of the throat portion 3 to 600 μm, the length of the diffuser portion 4 to 14.4 mm, and the inside diameter of the discharge portion 4 a of the diffuser portion 4 to 2.0 mm. The inside diameter of the drain pipes 5 was set to 0.45 mm.

In these experiments, water was used as the refrigerant, and an experimental system capable of adjusting experimental conditions was used, as described below. First, the pressure P_(s) of the steam flow in the introducing portion is adjustable in the range of 0.11 MPa to 0.15 MPa. In addition, in the introducing portion, the temperature T_(w0) of the liquid flow is adjustable in the range of 11.9° C. to 26° C., and a temperature T_(s0) of the steam flow is adjustable in the range of 101.4° C. to 111.2° C. The flow velocity m_(w0) of the liquid flow in the introducing portion is adjustable in the range of 1.59 ml/s to 2.20 ml/s (where, the density of the liquid flow is 958 kg/m³, for example). Dissolved oxygen amounts DO_(w) and DO_(s) of the introduced liquid flow and the introduced steam flow are adjustable in the range of 0.8 mg/l to 8.0 mg/l.

Experiment 1

Using the steam injector of Sample 3 (A_(s0)/A_(w0)=36.2, without drain pipes and check valves), the liquid flow, where T_(w0)=12.6° C., was first introduced. As a result, water in the liquid state was statically accumulated in the mixing portion and the throat portion of the steam injector. Then, in this state, the steam flow, where P_(s)=0.11 MPa and T_(s0)=102.3° C., was introduced. As a result, the liquid flowed in the mixing portion; the refrigerant flow was discharged from the discharge portion of the diffuser portion; and the operation of the steam injector was verified.

Experiment 2

Using the steam injector of Sample 4 (A_(s0)/A_(w0)=7.2, with drain pipes and check valves), the liquid flow, where T_(w0)=24.5° C., m_(w0)=1.59 ml/s, and DO_(w)=1.64 mg/l, was first introduced, and the steam flow was then introduced. As a result, the liquid flowed in the mixing portion; the refrigerant flow was discharged from the discharge portion of the diffuser portion; and the operation of the steam injector was verified. However, the operation was unstable in some cases.

FIG. 8 is a diagram showing pressures of the steam flows introduced during a stable operation and during an unstable operation and pressures thereof in a drain pipe. The horizontal axis represents time elapsed from the start of measurement. In FIG. 8, P_(in) represents the pressure in the drain pipe, and P_(s) represents the pressure of the steam flow. The text “Stable” means that the steam injector is in a stable operating state, and the text “Unstable” means that the steam injector is in an unstable operating state.

As shown in FIG. 8, during the stable operation, P_(in) was lower than P_(s), and the inside of the mixing portion was at a negative pressure. In contrast, during the unstable operation, P_(s) was lower than P_(in); the inside of the mixing portion was at a positive pressure; and the value of P_(s) was unstable. Thus, the steam flow was verified to be in the state of not being stably introduced.

Experiments 3-1, 3-2, and 3-3

Using the steam injector of Sample 7 (A_(s0)/A_(w0) being variable, with drain pipes and check valves), experiments were conducted, in each of which the liquid flow, where T_(w0)=21.7° C., m_(w0)=1.91 ml/s, and DO_(w)=2.4 mg/l, was first introduced, and the steam flow, where P_(s)=0.13 MPa and DO_(s)=3.5 mg/l, was then introduced. The ratio A_(s0)/A_(w0) was set to 4.4, 15.1, or 38.3.

As a result, the steam injector did not operate when A_(s0)/A_(w0)=4.4 and when A_(s0)/A_(w0)=38.3, but the refrigerant flow was discharged at a high discharge pressure from the discharge portion of the diffuser portion when A_(s0)/A_(w0)=15.1. Thus, the operation of the steam injector was verified.

In view of the results of further experiments conducted by the inventors of the present invention, a case is preferable in which the value of A_(s0)/A_(w0) is in the range of 7 to 30, inclusive, from the viewpoint of the operation of the steam injector, and another case is more preferable in which the value of A_(s0)/A_(w0) is in the range of 10 to 20, inclusive, from the viewpoint of the stable operation of the steam injector.

Second Embodiment

A second embodiment of the present invention will be described below. A steam injector according to the second embodiment includes a plurality of unit steam injectors each having the same structure as that of the steam injector 10 according to the first embodiment. The steam injector according to the second embodiment produces a high discharge pressure and a high discharge rate with a small-size by including the unit steam injectors producing a high discharge pressure with a small-size, and by joining together and discharging all the refrigerant flows discharged by the unit steam injectors at the high discharge pressure.

FIG. 9 is a schematic perspective view of the steam injector according to the second embodiment. This steam injector 100 is constituted by a plurality of (five in the second embodiment) plate-like component members 101, 102, 103, 104, and 105. A set of these plate-like component members 101, 102, 103, 104, and 105 are joined with one another in a stacked state. The plate-like component members 101 and 105 constitute the top layer and the bottom layer of the steam injector 100 having a layered structure.

A refrigerant liquid supply port 101 a for supplying the liquid flow W1 of the refrigerant from the outside and a refrigerant steam exhaust port 101 b for exhausting the steam flow S1 of the refrigerant to the outside are formed in the plate-like component member 101. A refrigerant liquid exhaust port 105 a for exhausting the liquid flow W1 to the outside and a refrigerant steam supply port 105 b for supplying the steam flow S1 from the outside are formed in the plate-like component member 105. A refrigerant flow discharge port 106 for discharging the refrigerant flows F1 is formed on the side surface of the steam injector 100.

FIG. 10 is a plan view of the plate-like component member 102. The area shaded with oblique lines in FIG. 10 represents a main surface of the plate-like component member 102. A plurality of grooves and holes are formed on the main surface of the plate-like component member 102. Such grooves and holes are also formed on a main surface of the plate-like component member 101 facing the component member 102, on both main surfaces of each of the plate-like component members 102, 103, and 104, and on a main surface of the plate-like component member 105 facing the component member 104. These grooves or holes include grooves or holes having shapes obtained by dividing into two halves the introducing portion, the mixing portion, the throat portion, and the diffuser portion of each of the unit steam injectors to be described later. The main surfaces of the plate-like component members 101, 102, 103, 104, and 105 facing one another are joined with one another so that the grooves or holes are combined with one another to form the unit steam injectors and flow passages for supplying or exhausting the refrigerant liquid and the refrigerant steam to or from the unit steam injectors.

Specifically, as shown in FIG. 10, a refrigerant liquid supply port 102 a, a refrigerant steam exhaust port 102 b, a refrigerant liquid exhaust port 102 c, and a refrigerant steam supply port 102 d are formed in the plate-like component member 102. Joining the plate-like component member 102 with the plate-like component member 103 forms three unit steam injectors 10′, a refrigerant liquid flow passage 102 e, a refrigerant steam flow passage 102 f, and a refrigerant flow joining passage 102 g. The refrigerant liquid supply port 102 a communicates with the refrigerant liquid supply port 101 a shown in FIG. 9. The refrigerant steam exhaust port 102 b communicates with the refrigerant steam exhaust port 101 b shown in FIG. 9. The refrigerant liquid exhaust port 102 c communicates with the refrigerant liquid exhaust port 105 a shown in FIG. 9. The refrigerant steam supply port 102 d communicates with the refrigerant steam supply port 105 b shown in FIG. 9. The refrigerant liquid supply port 102 a communicates with the refrigerant liquid exhaust port 102 c through the refrigerant liquid flow passage 102 e. The refrigerant steam exhaust port 102 b communicates with the refrigerant steam supply port 102 d through the refrigerant steam flow passage 102 f.

The unit steam injectors 10′ are arranged along main surfaces of the plate-like component members 101 and 102. The unit steam injectors 10′ are also arranged along the stacking direction of the plate-like component members 101, 102, 103, 104, and 105 because of being formed between respective adjacent pairs of the plate-like component members by joining together the set of plate-like component members 101, 102, 103, 104, and 105. In the steam injector 100, three unit steam injectors are formed along each pair of main surfaces, and four unit steam injectors are formed along the stacking direction. Accordingly, the steam injector 100 is an integrated set of a total of 12 unit steam injectors. When the numbers of the unit steam injectors arranged in the main surface direction and the stacking direction are denoted as N and M, respectively, it follows that N=3 and M=4 in the case of the steam injector 100. However, N may be one, and M may be two or greater; N may be two or greater and M may be one; or both N and M may be two or greater.

Each of the unit steam injectors 10′ includes the introducing portion 1, the mixing portion 2, the throat portion 3, and the diffuser portion 4, in the same way as in the case of the steam injector 10 according to the first embodiment.

The introducing portion 1 includes the nozzle-like liquid flow introducing portion 1 a and the steam flow introducing portion 1 b. The liquid flow introducing portion 1 a introduces the liquid flow W1 of the refrigerant supplied from the outside through the refrigerant liquid supply port 101 a, the refrigerant liquid supply port 102 a, and the refrigerant liquid flow passage 102 e. The steam flow introducing portion 1 b is formed on both sides of the liquid flow introducing portion 1 a, and introduces the steam flow S1 supplied through the refrigerant steam supply port 105 b, the refrigerant steam supply port 102 d, and the refrigerant steam flow passage 102 f. The liquid flow W1 is introduced in a jet-like manner by the nozzle-like liquid flow introducing portion 1 a. The refrigerant used is not particularly limited, but only needs to be a refrigerant, such as water or a chlorofluorocarbon-replacing material, which can be used in the heat pump device.

FIG. 11 is a main part sectional view of the steam injector 100, and shows a cross-sectional surface on a cross section corresponding to line A-A in FIG. 10. As shown in FIG. 11, the liquid flow introducing portion 1 a and the steam flow introducing portion 1 b are formed by combination of the grooves formed on the opposing main surfaces made when the plate-like component member 101 is joined with the plate-like component member 102.

FIG. 10 will be referred to back. In the same way as in the first embodiment, the mixing portion 2 has a shape with an internal cross-sectional area decreasing toward the moving direction of the refrigerant flow, that is, rightward in the plane of FIG. 10. While the cross section of the mixing portion 2 is rectangular in the second embodiment, the cross section may have another shape, such as a circular shape in the same way as in the first embodiment. The mixing portion 2 mixes therein the liquid flow with the steam flow to form the refrigerant flow in a gas-liquid mixing state. A negative pressure is produced in the mixing portion 2, and this phenomenon increases the flow velocity of the introduced steam flow.

As shown in FIG. 10, the steam flow S1 introduced through the steam flow introducing portion 1 b joins with the jet-like liquid flow W1 introduced through the liquid flow introducing portion 1 a from the circumferential side thereof, and mixes with the liquid flow W1.

In the same way as in the first embodiment, the throat portion 3 is formed on an outlet side of the mixing portion 2 and an inlet side of the diffuser portion 4. While the cross section of the throat portion 3 is rectangular in the second embodiment, the cross section may have another shape, such as a circular shape in the same way as in the first embodiment. The refrigerant flow has the highest flow velocity when passing through the throat portion 3.

In the same way as in the first embodiment, the diffuser portion 4 has a shape with an internal cross-sectional area increasing from the throat portion 3 toward the moving direction of the refrigerant flow. While the cross section of the diffuser portion 4 is rectangular in the second embodiment, the cross section may have another shape, such as a circular shape in the same way as in the first embodiment. In the diffuser portion 4, the refrigerant flow decreases in flow velocity and increases in pressure. As a result, the diffuser portion 4 discharges the refrigerant flow at the increased pressure as each of the refrigerant flows F1 from the discharge portion 4 a.

The refrigerant flow joining passage 102 g communicates with the discharge portions of the diffuser portions of the respective unit steam injectors 10′, and joins together the discharged refrigerant flows F1. The refrigerant flow discharge port 106 discharges the joined refrigerant flows F1 out of the steam injector 100.

FIG. 12 is a diagram for explaining the flow of the refrigerant. As shown in FIG. 12, the liquid flow W1 of the refrigerant is supplied from the refrigerant liquid supply port 101 a, and then supplied from the refrigerant liquid supply port formed in the plate-like component member 102 to the respective unit steam injectors formed by joining the plate-like component member 101 with the plate-like component member 102. A portion of the liquid flow not supplied to the respective unit steam injectors is discharged from the refrigerant liquid exhaust port, and supplied from the refrigerant liquid supply port formed in the plate-like component member 103 to the respective unit steam injectors formed by joining the plate-like component member 102 with the plate-like component member 103. In other words, the refrigerant liquid supply port of a plate-like component member communicates with the refrigerant liquid exhaust port of an adjacent plate-like component member, and thus forms a flow passage communicating the introducing portions of the unit steam injectors arranged along the stacking direction of the plate-like component members with one another. Subsequently, in the same way, the liquid flow is supplied to the respective unit steam injectors formed by joining together the plate-like component members, and the unused liquid flow is discharged outward from the refrigerant liquid exhaust port 105 a of the plate-like component member 105.

In the same way, the steam flow S1 of the refrigerant is supplied from the refrigerant steam supply port 105 b, and then supplied from the refrigerant steam supply port formed in the plate-like component member 104 to the respective unit steam injectors formed by joining the plate-like component member 105 with the plate-like component member 104. A portion of the steam flow not supplied to the respective unit steam injectors is discharged from the refrigerant steam exhaust port, and supplied from the refrigerant steam supply port formed in the plate-like component member 103 to the respective unit steam injectors formed by joining the plate-like component member 104 with the plate-like component member 103. Subsequently, in the same way, the steam flow is supplied to the respective unit steam injectors formed by joining together the plate-like component members, and the unused steam flow is discharged outward from the refrigerant steam exhaust port 101 b of the plate-like component member 101.

As described above, the steam injector 100 is an integrated set of the 12 unit steam injectors, and discharges the refrigerant flow obtained by joining together all the refrigerant flows discharged by the respective unit steam injectors. Each of the unit steam injectors 10′ has the same structure as that of the steam injector 10 according to the first embodiment. In the unit steam injector 10′, the internal cross-sectional area of the throat portion 3 is set smaller than the critical cross-sectional area at which the discharge pressure of the refrigerant flow nonlinearly increases. This setting increases the discharge pressure of the refrigerant flow discharged from the discharge portion 4 a of the diffuser portion 4 in the unit steam injector 10′ in the same way as in the steam injector 10. As a result, the steam injector 100 produces a high discharge pressure and a high discharge rate with a small-size.

FIG. 13 is a main part sectional view for explaining another embodiment of the introducing portion. As shown in FIG. 13, this introducing portion 1′ can be used in place of the introducing portion 1 shown in FIG. 10, and includes a heat-insulating layer 1 c interposed between the liquid flow introducing portion 1 a and the steam flow introducing portion 1 b. The heat-insulating layer 1 c can be structured, for example, as a layer filled with air between two walls or a vacuumized layer.

In the introducing portion 1, heating of the liquid flow W1 by the steam flow S1 reduces an effect of the liquid flow W1 for rapidly cooling to condense the steam flow S1 in the mixing portion 2. In contrast, in the introducing portion 1′, the heat-insulating layer 1 c prevents or mitigates the heating of the liquid flow W1 by the steam flow S1, so that the reduction in the condensing effect is prevented or mitigated.

The constituent material of the plate-like component members 101, 102, 103, 104, and 105 described above may be, for example, a resin material. However, a sufficient joining strength endurable to a discharge rate and a high discharge pressure of the refrigerant flow F1 is obtained by making these members from, for example, a metal, and by joining together the set of plate-like component members using, for example, the diffusion bonding. The metal material constituting the plate-like component members is preferably a material, such as a stainless material, having high heat insulating properties.

In the same way as in the case of the steam injector 10 according to the first embodiment, the unit steam injector 10′ may further include the drain pipes formed so as to communicate the inside of the mixing portion 2 with the external air. Exhausting the excess steam existing in the mixing portion 2 through the drain pipes increases the stability of operation of the unit steam injector 10′. The drain pipes may be provided with the check valves. The check valves serve to prevent the external air from being brought into the mixing portion 2 by the negative pressure produced during the operation of the unit steam injector 10′ so as to increase the stability of operation of the unit steam injector 10′.

The following describes steam injectors according to first to sixth modifications of the second embodiments.

First Modification

FIGS. 14A to 14D are schematic views for explaining the internal structure of a steam injector according to the first modification. FIG. 14A shows a steam injector 100A, and FIGS. 14B, 14C, and 14D show plate-like component members 102A, 103A, and 101A serving as components of the steam injector 100A. The steam injector 100A has a structure of a plurality of sets of stacked layers in which the plate-like component member 101A is interposed between each of a plurality of pairs of the plate-like component members 102A and 103A. These plate-like component members are, for example, made of a metal and joined together by the diffusion bonding.

FIG. 15 is a plan view of the plate-like component member 102A of FIG. 14B. In FIG. 15, the closely hatched areas represent grooves. The plate-like component member 103A has the same structure as that of the plate-like component member 102A. As shown in FIG. 15, in the plate-like component member 102A, a refrigerant liquid flow passage 102Ae, a refrigerant steam flow passage 102Af, a refrigerant flow joining passage 102Ag, and a refrigerant flow discharge port 106A are formed so as to penetrate through the plate-like component member 102A. The plate-like component member 102A includes grooves for constituting introducing portions 1A, mixing portions 2A, throat portions 3A, and diffuser portions 4A of unit steam injectors 10A. Joining the plate-like component member 102A with the plate-like component member 103A forms the unit steam injectors 10A. The plate-like component member 102A and the plate-like component member 103A may be stacked on each other so as to combine the grooves of one plate-like component member with those of the other plate-like component member, or may be stacked on each other so that a main surface of one of the plate-like component members provided with the grooves faces a main surface of the other of the plate-like component members not provided with the grooves.

Each of the unit steam injectors 10A includes corresponding ones of the introducing portions 1A, the mixing portions 2A, the throat portions 3A, and the diffuser portions 4A. Each of the introducing portions 1A includes a nozzle-like liquid flow introducing portion 1Aa and a steam flow introducing portion 1Ab. The liquid flow introducing portion 1Aa introduces the liquid flow of the refrigerant supplied from the outside through the refrigerant liquid flow passage 102Ae. The steam flow introducing portion 1Ab is formed on both sides of the liquid flow introducing portion 1Aa, and introduces the steam flow supplied through the refrigerant steam flow passage 102Af. The specific structure and the operation of each of the unit steam injectors 10A are substantially the same as those of the unit steam injector 10′. The internal cross-sectional area of each of the throat portions 3A is set smaller than the critical cross-sectional area at which the discharge pressure of the refrigerant flow nonlinearly increases, so that a higher discharge pressure is obtained.

FIG. 16 is a plan view of the plate-like component member 101A of FIG. 14D. As shown in FIG. 16, a refrigerant liquid flow passage 101Ae, a refrigerant steam flow passage 101Af, a refrigerant flow joining passage 101Ag, and the refrigerant flow discharge port 106A are formed in the plate-like component member 101A. The plate-like component member 101A is interposed between the plate-like component member 102A and the plate-like component member 103A, and serves as a spacer for securing flow passages of the refrigerant steam to the steam flow introducing portions 1Ab of the unit steam injectors 10A.

FIG. 17 is a perspective view of the plate-like component member 102A of FIG. 14B, and shows the plate-like component member 102A separated for ease of understanding of the structure of the grooves.

Second Modification

FIGS. 18A to 18D are schematic views for explaining the internal structure of a steam injector according to the second modification. FIG. 18A shows a steam injector 100B, and FIGS. 18B, 18C, and 18D show plate-like component members 102B, 103B, and 101B serving as components of the steam injector 100B. The steam injector 100B has a structure of a plurality of sets of stacked layers in which the plate-like component member 101B is interposed between each of a plurality of pairs of the plate-like component members 102B and 103B. These plate-like component members are, for example, made of a metal and joined together by the diffusion bonding.

FIG. 19 is a plan view of the plate-like component member 102B of FIG. 18B. In FIG. 19, the closely hatched areas represent grooves. The plate-like component member 103B has the same structure as that of the plate-like component member 102B. As shown in FIG. 19, in the plate-like component member 102B, a refrigerant liquid flow passage 102Be, a refrigerant steam flow passage 102Bf, a refrigerant flow joining passage 102Bg, and a refrigerant flow discharge port 106B are formed so as to penetrate through the plate-like component member 102B. The plate-like component member 102B includes grooves for constituting introducing portions 1B, mixing portions 2B, throat portions 3B, and diffuser portions 4B of unit steam injectors 10B. Joining the plate-like component member 102B with the plate-like component member 103B forms the unit steam injectors 10B. The plate-like component member 102B and the plate-like component member 103B may be stacked on each other so as to combine the grooves of one plate-like component member with those of the other plate-like component member, or may be stacked on each other so that a main surface of one of the plate-like component members provided with the grooves faces a main surface of the other of the plate-like component members not provided with the grooves.

Each of the unit steam injectors 10B includes corresponding ones of the introducing portions 1B, the mixing portions 2B, the throat portions 3B, and the diffuser portions 4B. Each of the introducing portions 1B includes a nozzle-like liquid flow introducing portion 1Ba and a steam flow introducing portion 1Bb. The liquid flow introducing portion 1Ba introduces the liquid flow of the refrigerant supplied from the outside through the refrigerant liquid flow passage 102Be. The steam flow introducing portion 1Bb is formed on both sides of the liquid flow introducing portion 1Ba, and introduces the steam flow supplied through the refrigerant steam flow passage 102Bf. The specific structure and the operation of each of the unit steam injectors 10B are substantially the same as those of the unit steam injector 10′. The internal cross-sectional area of each of the throat portions 3B is set smaller than the critical cross-sectional area at which the discharge pressure of the refrigerant flow nonlinearly increases, so that a higher discharge pressure is obtained.

FIG. 20 is a plan view of the plate-like component member 101B of FIG. 18D. As shown in FIG. 20, a refrigerant liquid flow passage 101Be, a refrigerant steam flow passage 101Bf, a refrigerant flow joining passage 101Bg, and the refrigerant flow discharge port 106B are formed in the plate-like component member 101B. The plate-like component member 101B is interposed between the plate-like component member 102B and the plate-like component member 103B, and serves as a spacer for securing flow passages of the refrigerant steam to the steam flow introducing portions 1Bb of the unit steam injectors 10B.

A through-groove 1Bc interposed between the liquid flow introducing portion 1Ba and the steam flow introducing portion 1Bb is further formed on the plate-like component member 102B. Such a through-groove 1Bc is also formed on the plate-like component member 101B. Moreover, the through-groove 1Bc is formed so as to be interposed also between the refrigerant liquid flow passage 102Be and the refrigerant steam flow passage 102Bf. The through-groove 1Bc forms an air layer serving as a heat-insulating layer for thermally insulating the liquid flow introducing portion 1Ba from the steam flow introducing portion 1Bb and also the refrigerant liquid flow passage 102Be from the refrigerant steam flow passage 102Bf. This air layer prevents or mitigates the heating of the liquid flow by the steam flow before the mixing, so that the reduction in the condensing effect in the mixing portion 2B is prevented or mitigated. The inside of the through-groove 1Bc may be in a vacuum state.

Third Modification

FIGS. 21A to 21D are schematic views for explaining the internal structure of a steam injector according to the third modification. FIG. 21A shows a steam injector 100C, and FIGS. 21B, 21C, and 21D show plate-like component members 102C, 103C, and 101C serving as components of the steam injector 100C. The steam injector 100C has a structure of a plurality of sets of stacked layers in which the plate-like component member 101C is interposed between each of a plurality of pairs of the plate-like component members 102C and 103C. These plate-like component members are, for example, made of a metal and joined together by the diffusion bonding.

FIG. 22 is a plan view of the plate-like component member 102C of FIG. 21B. In FIG. 22, the closely hatched areas represent grooves. The plate-like component member 103C has the same structure as that of the plate-like component member 102C. As shown in FIG. 22, in the plate-like component member 102C, a refrigerant liquid flow passage 102Ce, a refrigerant steam flow passage 102Cf, a refrigerant flow joining passage 102Cg, and a refrigerant flow discharge port 106C are formed so as to penetrate through the plate-like component member 102C. The plate-like component member 102C includes grooves for constituting introducing portions 1C, mixing portions 2C, throat portions 3C, and diffuser portions 4C of unit steam injectors 10C. Joining the plate-like component member 102C with the plate-like component member 103C forms the unit steam injectors 10C. The plate-like component member 102C and the plate-like component member 103C may be stacked on each other so as to combine the grooves of one plate-like component member with those of the other plate-like component member, or may be stacked on each other so that a main surface of one of the plate-like component members provided with the grooves faces a main surface of the other of the plate-like component members not provided with the grooves.

Each of the unit steam injectors 10C includes corresponding ones of the introducing portions 1C, the mixing portions 2C, the throat portions 3C, and the diffuser portions 4C. Each of the introducing portions 1C includes a nozzle-like liquid flow introducing portion 1Ca and a steam flow introducing portion 1Cb. The liquid flow introducing portion 1Ca introduces the liquid flow of the refrigerant supplied from the outside through the refrigerant liquid flow passage 102Ce. The steam flow introducing portion 1Cb is formed on both sides of the liquid flow introducing portion 1Ca, and introduces the steam flow supplied through the refrigerant steam flow passage 102Cf. The specific structure and the operation of each of the unit steam injectors 10C are substantially the same as those of the unit steam injector 10′. The internal cross-sectional area of each of the throat portions 3C is set smaller than the critical cross-sectional area at which the discharge pressure of the refrigerant flow nonlinearly increases, so that a higher discharge pressure is obtained. In each of the unit steam injectors 10C, the steam flow is mixed from the side surface in the moving direction of the refrigerant flow. In FIG. 22, a symbol 1Caa indicates a cross-sectional area through which the liquid flow is introduced during the mixing, and a symbol 1Cba indicates a cross-sectional area through which the steam flow is introduced during the mixing.

FIG. 23 is a plan view of the plate-like component member 101C of FIG. 21D. As shown in FIG. 23, a refrigerant liquid flow passage 101Ce, a refrigerant steam flow passage 101Cf, a refrigerant flow joining passage 101Cg, and the refrigerant flow discharge port 106C are formed in the plate-like component member 101C. The plate-like component member 101C is interposed between the plate-like component member 102C and the plate-like component member 103C, and serves as a spacer for securing flow passages of the refrigerant steam to the steam flow introducing portions 1Cb of the unit steam injectors 10C.

A through-groove 1Cc interposed between the liquid flow introducing portion 1Ca and the steam flow introducing portion 1Cb is formed on the plate-like component member 102C, in the same way as on the plate-like component member 102B. Such a through-groove 1Cc is also formed on the plate-like component member 101C. Moreover, the through-groove 1Cc is formed so as to be interposed also between the refrigerant liquid flow passage 102Ce and the refrigerant steam flow passage 102Cf. The through-groove 1Cc forms an air layer serving as a heat-insulating layer for thermally insulating the liquid flow introducing portion 1Ca from the steam flow introducing portion 1Cb and also the refrigerant liquid flow passage 102Ce from the refrigerant steam flow passage 102Cf. This air layer prevents or mitigates the heating of the liquid flow by the steam flow before the mixing, so that the reduction in the condensing effect in the mixing portion 2C is prevented or mitigated. The inside of the through-groove 1Cc may be in a vacuum state.

Fourth Modification

FIGS. 24A to 24D are schematic views for explaining the internal structure of a steam injector according to the fourth modification. FIG. 24A shows a steam injector 100D, and FIGS. 24B, 24C, and 24D show a plate-like component member 102D, nozzles 110D, and a plate-like component member 103D serving as components of the steam injector 100D. The steam injector 100D has a structure of a plurality of sets of stacked layers obtained by stacking a plurality of pairs of the plate-like component members 102D and 103D. These plate-like component members are, for example, made of a metal and joined together by the diffusion bonding.

FIGS. 25A to 25E are schematic views for explaining the structures of the plate-like component member and each of the nozzles of FIGS. 24B and 24C. FIG. 25A shows the plate-like component member 102D; FIGS. 25B, 25C, and 25D show the A-A line cross section, the B-B line cross section, and the C-C line cross section, respectively, of FIG. 25A; and FIG. 25E shows one of the nozzles 110D. In FIGS. 25A to 25D, the closely hatched areas represent grooves. The plate-like component member 103D has the same structure as that of the plate-like component member 102D.

As shown in FIGS. 25A to 25D, in the plate-like component member 102D, a refrigerant liquid flow passage 102De, a refrigerant steam flow passage 102Df, a refrigerant flow joining passage 102Dg, and a refrigerant flow discharge port 106D are formed so as to penetrate through the plate-like component member 102D. The plate-like component member 102D includes grooves for constituting mixing portions 2D, throat portions 3D, and diffuser portions 4D of unit steam injectors 10D. The plate-like component member 102D further includes grooves 102Dh for fitting the nozzles 110D therein. The nozzles 110D are fitted into the grooves 102Dh, and in that state, the plate-like component member 102D is joined with the plate-like component member 103D to form the unit steam injectors 10D. At this time, the nozzles 110D are also fitted into grooves formed on the plate-like component member 103D that are the same as the grooves 102Dh.

Each of the unit steam injectors 10D includes an introducing portion and corresponding ones of the mixing portions 2D, the throat portions 3D, and the diffuser portions 4D. The introducing portion includes a nozzle-like liquid flow introducing portion 1Da and a steam flow introducing portion 1Db. The liquid flow introducing portion 1Da introduces the liquid flow of the refrigerant supplied from the outside through the refrigerant liquid flow passage 102De. The steam flow introducing portion 1Db is formed so as to surround the liquid flow introducing portion 1Da, and introduces the steam flow supplied through the refrigerant steam flow passage 102Df. The specific structure and the operation of each of the unit steam injectors 10D are substantially the same as those of the unit steam injector 10′. The internal cross-sectional area of each of the throat portions 3D is set smaller than the critical cross-sectional area at which the discharge pressure of the refrigerant flow nonlinearly increases, so that a higher discharge pressure is obtained.

When the plate-like component member 102D is joined with the plate-like component member 103D in the state where the nozzles 110D are fitted in the grooves 102Dh, the nozzles 110D form the liquid flow introducing portions 1Da of the introducing portions, and grooves of the mixing portions 2D surrounding the nozzles 110D in the refrigerant steam flow passage 102Df serve as the steam flow introducing portions 1Db. The steam injector 100D includes a mechanism that allows the nozzles 110D to move in the grooves 102Dh and to be fixed in desired positions. Moving the positions of the nozzles 110D in the longitudinal direction of the grooves 102Dh can change the ratios of the cross-sectional areas between the liquid flow introducing portions 1Da and the corresponding steam flow introducing portions 1Db in the introducing portions.

Fifth Modification

FIGS. 26A to 26E are schematic views for explaining the internal structure of a steam injector according to the fifth modification. FIG. 26A shows a steam injector 100E, and FIGS. 26B, 26C, 26D, and 26E show plate-like component members 102E, 103E, and 104E, and 101E serving as components of the steam injector 100E. The steam injector 100E has a structure of a plurality of sets of stacked layers obtained by stacking a plurality of sets of the plate-like component members 102E, 103E, and 104E, and 101E. These plate-like component members are, for example, made of a metal and joined together by the diffusion bonding.

FIG. 27 is a plan view of the plate-like component member 103E of FIG. 26C. In FIG. 27, the closely hatched areas represent grooves. The plate-like component member 104E has the same structure as that of the plate-like component member 103E. As shown in FIG. 27, in the plate-like component member 103E, a refrigerant liquid flow passage 103Ee, a refrigerant steam flow passage 103Ef, a refrigerant flow joining passage 103Eg, and a refrigerant flow discharge port 106E are formed so as to penetrate through the plate-like component member 103E. The plate-like component member 103E includes grooves for constituting introducing portions 1E, mixing portions 2E, throat portions 3E, and diffuser portions 4E of unit steam injectors 10E. Moreover, in the plate-like component member 103E, wedge-shaped through-holes for constituting steam flow introducing portions 1Ec are formed and penetrate through the plate-like component member 103E.

FIG. 28 is a plan view of the plate-like component member 102E of FIG. 26B. The plate-like component member 101E has the same structure as that of the plate-like component member 102E. As shown in FIG. 28, a refrigerant liquid flow passage 102Ee, a refrigerant steam flow passage 102Ef, a refrigerant flow joining passage 102Eg, and the refrigerant flow discharge port 106E are formed in the plate-like component member 102E. The plate-like component member 102E includes grooves for constituting the steam flow introducing portions 1Ec communicating with the refrigerant steam flow passage 102Ef, grooves for constituting the throat portions 3E, and grooves for constituting flow passages 102Eh for letting out the refrigerant steam. The grooves for constituting flow passages 102Eh for letting out the refrigerant steam need not, however, be included.

Joining together the plate-like component members 102E, 103E, and 104E, and 101E forms the unit steam injectors 10E. Once the plate-like component members are joined together, the through-holes for constituting the steam flow introducing portions 1Ec formed in the plate-like component members 103E communicate with the grooves for constituting the steam flow introducing portions 1Ec formed in the plate-like component member 102E. The same through-holes and the same grooves are formed in the respective plate-like component members 104E and 101E, and the through-holes communicate with the grooves once these plate-like component members are joined together.

Each of the unit steam injectors 10E includes corresponding ones of the introducing portions 1E, the mixing portions 2E, the throat portions 3E, and the diffuser portions 4E. Each of the introducing portions 1E includes a nozzle-like liquid flow introducing portion 1Ea and steam flow introducing portions 1Eb and 1Ec. The liquid flow introducing portion 1Ea introduces the liquid flow of the refrigerant supplied from the outside through the refrigerant liquid flow passage 103Ee. The steam flow introducing portion 1Eb is formed on both sides of the liquid flow introducing portion 1Ea, and introduces the steam flow supplied through the refrigerant steam flow passage 103Ef.

Moreover, the steam flow introducing portion 1Ec is formed above and below the liquid flow introducing portion 1Ea, and introduces the steam flow supplied from the refrigerant steam flow passage through the grooves constituting the steam flow introducing portion 1Ec formed on the plate-like component members 102E and 101E (refer to FIG. 28) and further through the through-holes constituting the steam flow introducing portion 1Ec formed in the plate-like component members 103E and 104E (refer to FIG. 27). In other words, in each of the unit steam injectors 10E, the steam flow is introduced from four sides, that is, from the right and left sides and the upper and lower sides, of the liquid flow introducing portion 1Ea. If a portion of the refrigerant steam has passed through the grooves constituting the steam flow introducing portion 1Ec formed on the plate-like component members 102E and 101E, but has not passed through the through-holes constituting the steam flow introducing portion 1Ec formed in the plate-like component members 103E and 104E, the portion of the refrigerant steam is let out through the flow passage 102Eh to the refrigerant flow discharge port 106E.

The other parts of the specific structure and the operation of each of the unit steam injectors 10E are substantially the same as those of the unit steam injector 10′. The internal cross-sectional area of each of the throat portions 3E is set smaller than the critical cross-sectional area at which the discharge pressure of the refrigerant flow nonlinearly increases, so that a higher discharge pressure is obtained. Each of the unit steam injectors 10E introduces the refrigerant steam from the steam flow introducing portions 1Eb and 1Ec formed on the four sides of the liquid flow introducing portion 1Ea, and can thereby more efficiently introduce the refrigerant steam.

Sixth Modification

FIG. 29 is a schematic view for explaining the internal structure of a steam injector according to the sixth modification. This steam injector 200 is constituted by component members 201, 202, 203, 204, and 205. The component members 201, 202, 203, 204, and 205 are stacked and joined together to form nine unit steam injectors 10G extending along the stacking direction of the component members 201, 202, 203, 204, and 205. Each of the unit steam injectors 10G includes an introducing portion 1G, a mixing portion 2G, a throat portion 3G, and a diffuser portion 4G. The introducing portion 1G includes a nozzle-like liquid flow introducing portion 1Ga and a steam flow introducing portion 1Gb. These component members are, for example, made of a metal and joined together by the diffusion bonding.

The component member 201 includes a refrigerant liquid flow passage 200 e serving as a through-hole having a rectangular cross section. The component member 201 includes the refrigerant liquid flow passage 200 e and communicating holes 200 e 1 each communicating with the liquid flow introducing portion 1Ga of the introducing portion 1G formed by the component member 205 serving as a nozzle. The mixing portions 2G serving as cone-shaped through-holes are formed in the component member 202. Once the component members 201, 202, and 205 are joined together, a refrigerant steam flow passage 200 f is formed by the component member 201 and the component member 202. Moreover, the component members 205 are inserted into the mixing portions 2G, and the steam flow introducing portions 1Gb are formed in gaps between the component members 205 and the corresponding mixing portions 2G.

The diffuser portions 4G serving as cone-shaped through-holes are formed in the component member 203. Once the component member 202 is joined with the component member 203, the throat portions 3G are formed in positions by the joint surface between the component member 202 and the component member 203. Once the component member 203 is joined with the component member 204, a refrigerant flow joining passage 200 g and a refrigerant flow discharge port 206 are formed.

The other parts of the specific structure and the operation of each of the unit steam injectors 10G are substantially the same as those of the unit steam injector 10′. The internal cross-sectional area of the throat portion 3G is set smaller than the critical cross-sectional area at which the discharge pressure of the refrigerant flow nonlinearly increases, so that a higher discharge pressure is obtained. The unit steam injectors may be formed in this way so as to extend along the stacking direction of the component members that are stacked and joined together.

Third Embodiment

FIG. 30 is a block diagram of a heat pump device according to a third embodiment of the present invention. As shown in FIG. 30, this heat pump device 1000 includes the steam injector 100 according to the second embodiment, a compressor 20, a condenser 30, an evaporator 40, and a vapor-liquid separator 50. These components are connected together by piping serving as flow passages for circulating the refrigerant.

An operation of the heat pump device 1000 will be described. The compressor 20 uses electric power P from an outside source to compress the refrigerant steam supplied from the vapor-liquid separator 50. The condenser 30 discharges heat of the compressed refrigerant steam as heat H1, and condenses the refrigerant steam into the refrigerant liquid. The evaporator 40 applies heat H2 absorbed from the outside to the refrigerant liquid supplied from the vapor-liquid separator 50 to evaporate the refrigerant.

The steam flow of the refrigerant supplied from the evaporator 40 and the liquid flow of the refrigerant supplied from the condenser 30 are introduced into the steam injector 100, which in turn discharges the refrigerant flow at an increased pressure from the refrigerant flow discharge port 106 (refer to FIG. 9). The vapor-liquid separator 50 separates the liquid from the steam of the refrigerant included in the discharged refrigerant flow, and supplies the refrigerant steam to the compressor 20 while supplying the refrigerant liquid to the evaporator 40.

In the heat pump device 1000, the steam injector 100 can recover energy that is lost as vortices at an expansion valve in a heat pump device using the expansion valve. In addition, in the heat pump device 1000, the steam injector 100 reduces the load of the compressor 20, and can thereby reduce the amount of the electric power P to be supplied from the outside source to achieve a desired operating state. This causes the heat pump device 1000 to serve as a highly efficient heat pump device with an improved COP. The heat pump device 1000 can be used in various devices, such as air conditioners, refrigerators, and water heaters, which use heat pump devices, and thereby high-efficiency devices can be obtained.

Fourth Embodiment

FIG. 31 is a block diagram of a heat pump device according to a fourth embodiment of the present invention. As shown in FIG. 31, this heat pump device 2000 includes the steam injector 100 according to the second embodiment, the compressor 20, the condenser 30, the evaporator 40, the vapor-liquid separator 50, an expansion valve 60, and a pump 70. These components are connected together by piping serving as flow passages for circulating the refrigerant.

In the heat pump device 2000, the steam flow of the refrigerant supplied from the compressor 20 and the liquid flow of the refrigerant supplied at a pressure increased by the pump 70 from the vapor-liquid separator 50 are introduced to the steam injector 100, and the steam injector 100 discharges the refrigerant flow at an increased pressure from the refrigerant flow discharge port 106. The refrigerant flow at the increased pressure is supplied from the steam injector 100 to the condenser 30, which in turn releases the heat of the refrigerant flow as the heat H1, and condenses the refrigerant flow. The vapor-liquid separator 50 separates the liquid from the steam of the refrigerant included in the refrigerant flow from the condenser 30, and supplies the refrigerant steam to the expansion valve 60 while supplying the refrigerant liquid to the pump 70. The expansion valve 60 converts the refrigerant steam into the low-temperature, low-pressure refrigerant liquid. The evaporator 40 evaporates the refrigerant by applying the heat H2 absorbed from the outside to the refrigerant liquid reduced in temperature and pressure by the expansion valve 60. The compressor 20 uses the electric power P from the outside source to compress the refrigerant steam supplied from the vapor-liquid separator 50.

In this heat pump device 2000, the steam injector 100 assists the compressor 20 in compressing the refrigerant so as to supply the refrigerant at a desired pressure to the condenser 30. This results in a reduction in the amount of the electric power P to be supplied from the outside source to achieve a desired operating state. This, in turn, causes the heat pump device 2000 to serve as a highly efficient heat pump device with an improved COP. The heat pump device 2000 can be used in various devices, such as the air conditioners, the refrigerators, and the water heaters, which use heat pump devices, and thereby high-efficiency devices can be obtained.

In the heat pump devices 1000 and 2000 of the third and fourth embodiments described above, the steam injector 100 can be replaced with the steam injector according to any of the first to fifth modifications or the steam injector 10 according to the first embodiment.

The embodiments described above are not intended to limit the present invention. The present invention also includes embodiments structured by appropriately combining the components describe above. Further effects and modifications can be easily derived by those skilled in the art. The embodiments described above are not intended to limit the broader aspects of the present invention, and various modifications can be made.

REFERENCE SIGNS LIST

-   -   1, 1′, 1A, 1B, 1C, 1E, 1G Introducing portion     -   1 a, 1Aa, 1Ba, 1Ca, 1Da, 1Ea, 1Ga Liquid flow introducing         portion     -   1 b, 1Ab, 1Bb, 1Cb, 1Db, 1Eb, 1Ec, 1Gb Steam flow introducing         portion     -   1Bc, 1Cc Through-groove     -   2, 2A, 2B, 2C, 2D, 2E, 2G Mixing portion     -   3, 3A, 3B, 3C, 3D, 3E, 3G Throat portion     -   4, 4A, 4B, 4C, 4D, 4E, 4G Diffuser portion     -   4 a Discharge portion     -   5 Drain pipe     -   6 Check valve     -   10, 100, 100A, 100B, 100C, 100D, 100E, 200 Steam injector     -   10′, 10A, 10B, 10C, 10D, 10E, 10G Unit steam injector     -   20 Compressor     -   30 Condenser     -   40 Evaporator     -   50 Vapor-liquid separator     -   60 Expansion valve     -   70 Pump     -   101, 101A, 101B, 101C, 101E, 102, 102A, 102B, 102C, 102D, 102E,         103, 103A, 103B, 103C, 103D, 103E, 104, 104E, 105 Plate-like         component member     -   101 a, 102 a Refrigerant liquid supply port     -   101 b, 102 b Refrigerant steam exhaust port     -   102 c, 105 a Refrigerant liquid exhaust port     -   102 d, 105 b Refrigerant steam supply port     -   101Ae, 101Be, 101Ce, 102 e, 102Ae, 102Be, 102Ce, 102De, 102Ee,         103Ee, 200 e Refrigerant liquid flow passage     -   101Af, 101Bf, 101Cf, 102 f, 102Af, 102Bf, 102Cf, 102Df, 102Ef,         103Ef, 200 f Refrigerant steam flow passage     -   101Ag, 101Bg, 101Cg, 102 g, 102Ag, 102Bg, 102Cg, 102Dg, 102Eg,         103Eg, 200 g Refrigerant flow joining passage     -   102Dh Groove     -   102Eh Flow passage     -   106, 106A, 106B, 06C, 106D, 106E, 206 Refrigerant flow discharge         port     -   110D Nozzle     -   201, 202, 203, 204, 205 Component member     -   200 e 1 Communicating hole     -   1000, 2000 Heat pump device     -   C1, C2 Region     -   F1 Refrigerant flow     -   H1, H2 Heat     -   P Electric power     -   S1 Steam flow     -   W1 Liquid flow 

1: A steam injector comprising: an introducing portion introducing a liquid flow of a refrigerant and a steam flow of the refrigerant; a mixing portion that has a shape with an internal cross-sectional area decreasing toward a moving direction of the liquid flow, and internally mixes the jet-like liquid flow with the steam flow to form a refrigerant flow; a throat portion formed on an outlet side of the mixing portion; and a diffuser portion that has a shape with an internal cross-sectional area increasing from the throat portion toward a moving direction of the refrigerant flow, and discharges the refrigerant flow at an increased pressure from a discharge portion, wherein the throat portion has an internal cross-sectional area smaller than a critical cross-sectional area at which a discharge pressure of the refrigerant flow discharged from the discharge portion of the diffuser portion nonlinearly increases when the internal cross-sectional area of the throat portion is reduced. 2: The steam injector according to claim 1, wherein the internal cross-sectional area of the throat portion is an internal cross-sectional area at which the first-order differential coefficient of a curve representing a change in the discharge pressure of the refrigerant flow with respect to a change in the internal cross-sectional area of the throat portion is smaller than zero, or the second-order differential coefficient of the curve is larger than zero. 3: The steam injector according to claim 1, wherein the following Expression (1) is satisfied: P _(D)=(m _(w0) ·u _(w0))/A ₁+(m _(s0) ·u _(s0))/A ₁−(m ₁ ·u ₁)/A ₁+(1−ζ_(N))·(ρ·u ₁ ²/2)−(ζ_(T)+ζ_(D))·(ρ_(w) ·u ₁ ²/2)  (1) where A₁ denotes the internal cross-sectional area of the throat portion; m_(w0) and u_(w0) denote a mass flow rate and a flow velocity, respectively, of the liquid flow in the introducing portion; m_(s0) and u_(s0) denote a mass flow rate and a flow velocity, respectively, of the steam flow in the introducing portion; m₁ and u₁ denote a mass flow rate and a flow velocity, respectively, of the refrigerant flow in the throat portion; □_(N), □_(T), and □_(D) denote pressure loss coefficients in the mixing portion, the throat portion, and the diffuser portion, respectively; □_(w) denotes a density of the liquid flow; and P_(D) denotes the discharge pressure of the refrigerant flow in the discharge portion. 4: The steam injector according to claim 1, wherein the throat portion has a circular internal cross section, and the internal cross section has a diameter of 2 mm or smaller. 5: The steam injector according to claim 4, wherein a diameter of the internal cross section is 1 mm or smaller. 6: The steam injector according to claim 1, wherein A_(s0)/A_(w0) is in a range of 7 to 30, inclusive, where A_(w0) denotes a cross-sectional area of a region in the mixing portion into which the liquid flow is introduced, and A_(s0) denotes a cross-sectional area of a region in the mixing portion into which the steam flow is introduced. 7: The steam injector according to claim 6, wherein the value of As0/Aw0 is in a range of 10 to 20, inclusive. 8: The steam injector according to claim 1, further comprising a drain pipe formed so as to communicate inside of the mixing portion with external air. 9: The steam injector according to claim 8, wherein the drain pipe is provided with a check valve. 10: The steam injector according to claim 1, wherein the refrigerant is water or a chlorofluorocarbon-replacing material. 11: A steam injector comprising: a plurality of unit steam injectors each serving as the steam injector as claimed in claim 1; a liquid flow passage and a steam flow passage for supplying the liquid flows and the steam flows of the refrigerant to the respective introducing portions of the corresponding unit steam injectors. 12: The steam injector according to claim 11, wherein the steam injector is formed by joining together a set of component members, and grooves or holes having shapes obtained by dividing the introducing portion, the mixing portion, the throat portion, and the diffuser portion into a plurality of parts thereof are formed in each of the set of component members, and the introducing portion, the mixing portion, the throat portion, and the diffuser portion are formed by the grooves or holes when the set of component members are joined together. 13: The steam injector according to claim 12, wherein the set of component members have a plate-like shape and are joined with one another in a stacked state, and at least two of the unit steam injectors are arranged along main surfaces of the plate-like component members. 14: The steam injector according to claim 13, wherein a flow passage is formed that communicates together the introducing portions of the unit steam injectors arranged along the main surfaces of the plate-like component members. 15: The steam injector according to claim 12, wherein the set of component members have a plate-like shape and are joined with one another in a stacked state, and at least two of the unit steam injectors are arranged along a stacking direction of the plate-like component members. 16: The steam injector according to claim 15, wherein a flow passage is formed that communicates together the introducing portions of the unit steam injectors arranged along the stacking direction of the plate-like component members. 17: The steam injector according to claim 12, wherein the set of component members are joined with one another in a stacked state, and the unit steam injectors extend along the stacking direction of the component members. 18: The steam injector according to claim 11, wherein the set of component members are joined together by diffusion bonding. 19: A heat pump device comprising: a compressor compressing a refrigerant; a condenser condensing the refrigerant; an evaporator evaporating the refrigerant; and the steam injector as claimed in claim 1 that introduces the steam flow of the refrigerant and the liquid flow of the refrigerant, and discharges the refrigerant flow at the increased pressure from the discharge portion of the diffuser portion. 